1. Field
The present disclosure relates to swing analyses, and more specifically relates to swing analyses using motion sensors.
2. Description of Related Art
Exemplary conventional devices for analyzing swings of objects such as sports equipment (e.g., golf clubs or baseball bats) include camera-equipped devices that capture successive images of the moving object, to which a marker is attached, until another object (e.g., a ball) is hit. Such devices are able to analyze the swing of the object based on captured images. However, such devices are limited by information that can be conveyed through images, and thus may be unable to perform certain detailed analyses. Such devices are also typically large in size, and thus may be limited in portability.
In an Internet article titled “THE DESIGN AND APPLICATION OF WIRELESS MEMS INERTIAL MEASUREMENT UNITS FOR THE MEASUREMENT AND ANALYSIS OF GOLF SWINGS,” Kevin W. King describes a technique for performing swing analysis that addresses certain limitations of conventional, image-based swing analyzers. More specifically, King describes embedding a swing analysis device into the grip of a golf club that includes a compact motion sensor, a battery, and a communication module arranged in series. King further describes that, when the golf club is swung by a swing machine, data output from the compact motion sensor can be analyzed by the swing analysis device.
King's swing analyses are based on a swing machine, which provides consistent and correctly postured swings. King does not, however, consider the errors that could be introduced by human golfers or by mass-produced motion sensors.
As one example, under King's swing analysis technique, a direction that is orthogonal to a face of the golf club, at address, is used as a target line. As one of ordinary skill in the art would appreciate, a target line is an imaginary line from a golf ball to a target. The target line is useful as a reference for measuring the angle of a swing path and/or characterizing whether a swing path is inside-out, outside-in, or inside-in, among other things. The swing path of a golf club is defined as the trajectory of the head of the golf club as viewed from directly above. In King, the direction orthogonal to the face of the golf club is invariably be used as the target line because King's swing machine can take consistent address postures between swings and correct align the club face towards target each time. In contrast, it is difficult for a human golfer to have consistent postures at each swing, and/or to accurately align the face of a golf club in the direction of the target each time. King's technique does not address how an accurate target line, which is needed to accurately analyze a swing path, can be determined under these circumstances.
Moreover, King's swing analysis technique does not correct for errors that are introduced by its motion sensors. Since motion sensors are machines, they are subject to manufacturing tolerances that are caused by deviations in output. Also, motion sensors are susceptible heat buildup that can introduce output errors.
Furthermore, King's swing analysis technique assumes that a swing is made immediately after a golf club is positioned at address. In contrast, human golfers typically do not swing immediately after the address state. Rather, human golfers typically perform pre-swing movements (hereafter referred to as “waggles”) before the start of a swing. The use of measurement data that is based on waggles in swing analyses can introduce errors in the corresponding results.